Robinhood - Free stock trading service.
E*Trade Web Platform - E*Trade Web Platform is a program that allows users to trade stocks, options, and other securities.
Stonksfolio - Gain insight into the performance of stock & ETF investments
Calypso Platform - Calypso Platform is a comprehensive solution for trading, risk management, and regulatory compliance.
Bux - Casual stock trading - thumb swipes only
White Label MT4/MT5 - White Label MT4/MT5 is a tool for brokers that want to provide their clients with a customized trading experience.